United States · 1991–2020

Best time to visit
Wonder Lake.

September leads for comfortable weather in Wonder Lake: typically 23.4°C by day, 10.9°C at night, with 91 mm of rain. Based on measured 1991–2020 NOAA station history.

Best comfortSeptember

Typical high23.4°C

Typical low10.9°C

Rain in September91 mm

Comfort

September

September · August · June

79climate match

Beach

July

July · August · June

69climate match

Outdoors

September

September · May · October

74climate match

The weakest month is January, scoring 5 against September’s 79 — days reach only -1.7°C, 26° below the 24°C the score treats as ideal.

Month by month

The whole year,
without the guesswork.

The bars show the comfort score. Day and night temperatures come from daily observed highs and lows; rain is the historical monthly estimate.

Jan

5-1.7° / -10.6°

Feb

50.4° / -9.1°

Mar

56.9° / -3.4°

Apr

3114.1° / 2.6°

May

5820.3° / 8.5°

Jun

7325.8° / 14°

Jul

7128.2° / 16.5°

Aug

7627.1° / 15.5°

Sep

7923.4° / 10.9°

Oct

4516.4° / 4.3°

Nov

138.2° / -1.3°

Dec

51.2° / -7.1°

Monthly climate evidence for Wonder Lake — daylight is calculated from latitude, everything else is measured, sea temperature from the nearest open water 39 km away
Month	Day	Night	Rain	Wet days	Sea	Daylight	Comfort	Coverage
January	-1.7°C	-10.6°C	37 mm	6	3.4°C	9 h 24	5	Strong coverage
February	0.4°C	-9.1°C	43 mm	6	2.2°C	10 h 29	5	Strong coverage
March	6.9°C	-3.4°C	53 mm	6.8	2.1°C	11 h 48	5	Strong coverage
April	14.1°C	2.6°C	93 mm	9.4	3.5°C	13 h 18	31	Strong coverage
May	20.3°C	8.5°C	118 mm	10.4	6.2°C	14 h 34	58	Strong coverage
June	25.8°C	14°C	127 mm	9.8	12.9°C	15 h 16	73	Strong coverage
July	28.2°C	16.5°C	97 mm	7.6	20.1°C	14 h 59	71	Strong coverage
August	27.1°C	15.5°C	96 mm	8.1	21.8°C	13 h 54	76	Strong coverage
September	23.4°C	10.9°C	91 mm	6.8	19.4°C	12 h 26	79	Strong coverage
October	16.4°C	4.3°C	80 mm	7.8	13.8°C	10 h 59	45	Strong coverage
November	8.2°C	-1.3°C	56 mm	5.9	8.5°C	9 h 43	13	Strong coverage
December	1.2°C	-7.1°C	46 mm	6.2	5.3°C	9 h 05	5	Strong coverage

Records at MCHENRY STRATTON LOCK/DAM, 1992–2026
Month	Record high	Record low	Wettest day	Wettest / driest month	Years
January	16.7°C8 Jan 2008	-35.6°C31 Jan 2019	44 mm14 Jan 1995	97 mm2013 · driest 3 mm in 2014	34
February	25.6°C28 Feb 2024	-30.6°C3 Feb 1996	52 mm21 Feb 1997	93 mm1997 · driest 3 mm in 2003	33
March	28.3°C21 Mar 2012	-25.0°C5 Mar 2015	49 mm9 Mar 2009	116 mm2020 · driest 16 mm in 1999	33
April	32.2°C19 Apr 2002	-10.0°C8 Apr 2018	97 mm18 Apr 2013	239 mm2026 · driest 27 mm in 2021	33
May	37.2°C28 May 2018	-3.3°C9 May 2020	72 mm18 May 2004	260 mm2004 · driest 25 mm in 1994	32
June	37.8°C15 Jun 2022	1.7°C1 Jun 1993	112 mm26 Jun 2013	263 mm1993 · driest 31 mm in 2012	34
July	38.3°C14 Jul 1995	6.7°C2 Jul 2001	102 mm23 Jul 2011	214 mm2011 · driest 14 mm in 2002	33
August	36.7°C28 Aug 2024	4.4°C31 Aug 2009	106 mm7 Aug 2007	323 mm2007 · driest 23 mm in 2003	33
September	35.6°C23 Sep 2017	-2.2°C30 Sep 1993	116 mm12 Sep 2019	309 mm2019 · driest 2 mm in 2017	33
October	32.2°C4 Oct 2025	-5.6°C31 Oct 2020	68 mm18 Oct 1998	187 mm2001 · driest 11 mm in 2005	32
November	25.6°C11 Nov 2022	-15.6°C29 Nov 1995	46 mm11 Nov 1995	147 mm1994 · driest 10 mm in 1999	33
December	20.0°C6 Dec 2001	-28.3°C25 Dec 2000	43 mm10 Dec 2003	117 mm2008 · driest 10 mm in 2005	32

Typical days per month at MCHENRY STRATTON LOCK/DAM, 1991–2020
Month	Days 25°C+	Days 30°C+	Frost nights	Heavy rain (10 mm+)	Snow days
January	0	0	29	1	7
February	0	0	26	1	5
March	<1	0	23	2	3
April	2	<1	9	3	<1
May	8	2	1	4	0
June	18	7	0	4	0
July	26	11	0	3	0
August	23	7	0	3	0
September	13	3	<1	3	0
October	3	<1	8	3	0
November	0	0	19	2	1
December	0	0	27	1	5

How often, not how much — every day in MCHENRY STRATTON LOCK/DAM’s record sorted by what it was actually like, rather than averaged
Month	Warm & dry days	Wet days	Washouts	Week with 3+ wet days	Daytime mean has ranged
January	0%	20%	3%	17%	-4.0–1.3°C
February	<1%	21%	4%	17%	-3.5–5.0°C
March	5%	24%	6%	26%	3.6–11.0°C
April	14%	32%	10%	39%	11.6–17.0°C
May	38%	30%	11%	38%	18.4–22.9°C
June	62%	30%	12%	37%	24.2–28.1°C
July	74%	25%	10%	25%	26.4–30.4°C
August	73%	26%	10%	28%	25.1–29.3°C
September	61%	24%	9%	28%	21.3–26.0°C
October	24%	23%	7%	24%	15.0–19.3°C
November	5%	21%	6%	20%	4.2–12.4°C
December	<1%	21%	5%	20%	-1.9–5.2°C

A warm and dry day reaches 20°C with under 1 mm of rain; a wet day gets 1 mm or more; a washout gets 10 mm or more. The week column is the share of seven-day stretches in that month, across the station’s whole daily record, that contained three or more wet days — the odds a week-long trip is rained on repeatedly, counted rather than modelled. The last column is the 10th to 90th percentile of that month’s daytime average across individual years: a narrow band means the average is what you will get, a wide one means the average is a midpoint between years that felt quite different.

1994Each stripe is one year’s mean temperature against the 27-year average. Warmest: 2024. Coolest: 2014.2025

The evidence behind this page

Nearby, measured,
and named.

Place identity: GeoNames 4916973
NOAA station: USC00115493 · MCHENRY STRATTON LOCK/DAM
Station distance: 11.4 km from the place centre
Climate period: 1991–2020
Minimum month coverage: 26 usable years
Daylight: Calculated from latitude 42.39°, mid-month, sunrise to sunset including refraction. Not a station measurement.
Sea temperature: NOAA OISST v2.1 1991–2020 monthly climatology, nearest open water 39 km from the place centre. A sheltered bay can run warmer than the open sea it is measured from.
Important limit: Historical climate is not a forecast. Nearby stations can miss mountains, coasts, and local microclimates.

These places read the same station, so their numbers are identical — distance from MCHENRY STRATTON LOCK/DAM is what differs

Crystal Lake→McHenry→Cary→Island Lake→Johnsburg→Lakemoor→

Or put two places side by side: Wonder Lake vs Crystal Lake

Best time to visitWonder Lake.

September

July

September

The whole year,without the guesswork.

Nearby, measured,and named.

Best time to visit
Wonder Lake.

The whole year,
without the guesswork.

Nearby, measured,
and named.